from.optional is not optional, it became required.

[XuPengfei-1020]

Rule From.modifiers must with a optional or it will not work.
OS version: 15.2 (24C101)
karabiner version: 15.3.0

Test rule:

{
    "description": "ctrl + c -> cmd + c",
    "manipulators": [
        {
            "from": {
                "key_code": "c",
                "modifiers": {
                    "mandatory": ["left_control"],
                    // "optional": ["any"] // If I comment this line, this rule will not work.
                }
            },
            "to": [
                {
                    "key_code": "c",
                    "modifiers": ["left_command"]
                }
            ],
            "type": "basic"
        }
    ]
}

[tekezo]

This is by design. If optional is not specified, the modification only takes effect when the specified modifier state.
https://karabiner-elements.pqrs.org/docs/json/complex-modifications-manipulator-definition/from/modifiers/#examples

[XuPengfei-1020]

@tekezo Thanks for your replay.

If optional is not specified, the modification only takes effect when the specified modifier state.

Could you please explain more about this rule?

https://karabiner-elements.pqrs.org/docs/json/complex-modifications-manipulator-definition/from/modifiers/#with-modifiersmandatory
Here given a example of mapping control + h to delete_or_backspace , without from. modifiers.optional.
Can I map control + h to command + h without from. modifiers.optional?

Thank you.

[tekezo]

Can I map control + h to command + h without from. modifiers.optional?

Specify to.modifiers:

{
    "description": "example",
    "manipulators": [
        {
            "from": {
                "key_code": "h",
                "modifiers": { "mandatory": ["control"] }
            },
            "to": [
                {
                    "key_code": "h",
                    "modifiers": ["left_command"]
                }
            ],
            "type": "basic"
        }
    ]
}

[XuPengfei-1020]

I know what this bug is.

If I set a rule like below (with out specify "optional": ["any"] in manipulators.from), this rule will be volatile.
It work firstly, but lose efficacy a few minutes later.
Everytime after I restart the karabiner, this rule will work as expect for few minutes (but then become volatile).

And, if I add a "optional": ["any"] in manipulators.from on this rule, the bug is disappeared, this rule will always work as expect.

Can I map control + h to command + h without from. modifiers.optional?

Specify to.modifiers:

{
    "description": "example",
    "manipulators": [
        {
            "from": {
                "key_code": "h",
                "modifiers": { "mandatory": ["control"] }
            },
            "to": [
                {
                    "key_code": "h",
                    "modifiers": ["left_command"]
                }
            ],
            "type": "basic"
        }
    ]
}

[tekezo]

Maybe a modifier key is unintentionally stuck?
When the rule stops working, what do the flags show in EventViewer?